1. The Field of the Invention
The present invention relates generally to biodegradable polymers or polymer blends and sheets manufactured therefrom. More particularly, the present invention relates to fibrous sheets that are coated or impregnated with biodegradable polymers or blends that render the sheets more resistant to liquids. The resulting sheets are suitable for a number of applications, such as disposable wraps, bags, pouches or other packaging materials.
2. The Relevant Technology
As affluence grows, so does the ability to purchase and accumulate more things. Never before in the history of the world has there been such a large number of people with such tremendous buying power. The ability to purchase relatively inexpensive goods, such as books, tools, toys and food, is a luxury enjoyed by virtually all levels of society, even those considered to be at the poorer end of the spectrum. Because a large percentage of what is purchased is prepackaged, there has been a tremendous increase in the amount of disposable packaging materials that are routinely discarded into the environment as solid waste. Thus, as society becomes more affluent, it generates more disposable trash.
Some packaging materials are only intended for a single use, such as boxes, cartons, pouches, bags and wraps used to package items purchased from wholesale and retail outlets. Even the advent of computers and “paperless” transactions has not stemmed the rising tide of packaging wastes. Indeed, the onset of “e-commerce” has spawned a great mail-order fad, thus creating a whole new market of individually packaged and shipped items.
Moreover, the modern, fast-paced lifestyle has greatly disrupted traditional eating routines in which people prepared their own meals and sat down as a family or group. Instead, people grab food on the run, thus creating ever-increasing amounts of fast-food packaging materials that are used once and then discarded. In view of the high volume of disposable packaging materials being generated, some countries, particularly those in Europe, have mandated either the recycling of fast food generated wastes or the use of packaging materials which are “biodegradable” or “compostable”. Environmental activists commonly pressure companies that generate solid waste to find more environmentally friendly alternatives. There is therefore an ever-present need to develop biodegradable alternatives to nonbiodegradable packaging materials.
Paper, paperboard and other fibrous sheets made from natural cellulose-based fibers are biodegradable. However, fibrous sheets tend to be porous. As a result, they do not provide good barriers against water, oil or other liquids. When fibrous sheets are used in applications where they will be exposed to liquids, they must generally be treated with a liquid-resistant material, such as paraffin wax or plastic. By doing so, however, the fibrous sheets are no longer biodegradable, but are as resistant to degradation as plastic or paraffin wax.
In view of the foregoing, it would be an advancement in the art to provide fibrous sheets that were resistant to liquids and that were biodegradable. In addition or alternatively, it would be a further advancement in the packaging art to provide improved fibrous sheets that were not only resistant to liquids, but still had good breathability and water vapor transmission compared to conventional fibrous sheets treated with wax or plastic.